How long should a shaft be to get an extremely high success rate for obtaining mitochondrial DNA that can be used in an investigation?

It’s letter b because the area of the trapezoid is 72

The earth's inner core is the earth's innermost part. it is primarily a solid ball with a radius of about 1,220 km (760 miles), which is about 70% of the moon's radius.[1][2] it is composed of an iron–nickel alloy and some light elements. the temperature at the inner core's surface is approximately 5,700 k (5,430 °c), which is about the temperature at the surface of the sun.